Can BNU share interrupts?
This translates to:”can I configure two ports to use the same IRQ”? The short answer is No. The long answer is that there are two problems involved. The first one is support in hardware: The design of the AT bus prevents any two cards from using the same interrupt. Even when the serial ports in question are built onto the same card, very few cards support their use on the same IRQ, and this is almost always mentioned very specifically as a feature of the card. If the documentation does not metion IRQ sharing, then it almost invariably won’t work. Some cards however, do support IRQ sharing – notably the AST 4-port, 4 and 8 port “dumb” DigiBoard and the Computer Decisions 4-port. There is also no problem sharing IRQ levels on a level triggered bus, such as provided by the MCA (PS/2) bus architecture. The second problem is that BNU does not support IRQ chaining. It looks only at one port when servicing interrupts. However, interrupt sharing will be supported in a future release.
